CHECAL-TERMS PDF - Engineering Definitions

Dimensions: General expressions of characteristics of measurement, such as length, time, mass, and temperature. Units: Means of explicitly expressing dimensions, e.g., feet and meter for length. Fundamental Dimension: Measured independently and sufficient to describe physical quantities like lengt...

Dimensions: General expressions of characteristics of measurement, such as length, time, mass, and temperature. Units: Means of explicitly expressing dimensions, e.g., feet and meter for length. Fundamental Dimension: Measured independently and sufficient to describe physical quantities like length, mass, time, and temperature. Derived Dimension: Developed in terms of fundamental dimensions; units are combinations of fundamental dimension units. Système Internationale d’Unitès (SI): The most commonly used system of units, also called the MKS system. CGS system: Uses centimeters, grams, and seconds as the units for length, mass, and time, respectively. American Engineering System (AES): Uses feet, pounds, and seconds as units for length, mass, and time, respectively. SI Base Units: The standard units in the SI system, such as meter for length, kilogram for mass, and second for time. SI Derived Units: Units derived from base units, like square meters for area and joules for energy. SI Prefixes: Prefixes used to express multiples or fractions of units, like kilo (10^3) and milli (10^-3). Unit Conversion: Process of converting a quantity from one unit to another using conversion factors. Dimensional Homogeneity: Principle stating that equations must have the same net dimensions on both sides. Interpolation: Estimating the value of a dependent variable within the range of calibration data. Extrapolation: Estimating the value of a dependent variable outside the range of calibration data. Curve fitting is the process of fitting a calibration data to a curve defined by a known mathematical function. Linear curve fitting is the process of fitting a calibration data to a straight line defined as: y = mx + b Process refers to any operation or series of operations by which a particular objective is accomplished. Process Variables: Parameters measured in a process, such as temperature, pressure, flow rate, and composition. Temperature: A measure of the average kinetic energy of particles in a body, perceived as hotness or coldness. Resistance thermometer: based on electrical resistance of a conductor Thermocouple: based on voltage at the junction of two dissimilar metals Pyrometer: based on the spectra of emitted radiation Thermometer: based on the volume of a fixed mass of fluid Temperature scale is defined by arbitrarily assigning numerical values to two reproducibly measurable temperatures. Pressure: The normal force per unit area exerted on a surface. Hydrostatic pressure P is the pressure at the base of a column of static fluid. Absolute pressure is the pressure relative to zero pressure or a vacuum. Gage pressure is the pressure relative to atmospheric pressure. A gage pressure of zero indicates that the absolute pressure of the fluid is equal to atmospheric pressure. Vacuum pressure is the difference between the atmospheric pressure and the absolute pressure. Bourdon gauge most common mechanical device for pressure measurement; primarily used to pressure moderate to high pressures; reads the gauge pressure of a fluid Manometer is a tube partially filled with a fluid of known density (the manometer fluid). Manometers are typically used for pressures below 3 atm. Open-end manometer is a manometer with one end exposed to a fluid whose pressure is to be measured and the other is open to the atmosphere. Differential manometer is used to measure the pressure difference between two points in a process line Sealed-end manometer or barometer is exposed to near-vacuum at one end and to the fluid whose pressure is to be measured at the other end. If open end is exposed to the atmosphere Density is the mass per unit volume of a substance. Specific volume of a substance is the volume occupied by a unit mass of a substance; it is the inverse of density Specific Gravity: Ratio of the density of a substance to the density of a reference substance, typically water. Baumé scale uses two scales for measuring density, one for liquids less dense than water and one for liquids denser than water. Twaddell scale is used for liquids heavier than water. Brix scale is used to indicate the strength of sugar solution. This scale is defined such that the density of 1.0 wt% aqueous sugar solution is equivalent to one degree Brix. American Petroleum Institute (API) scale compares the specific gravity of a petroleum liquid compared to water. Mass Fraction: A way to express the composition of a mixture based on the ratio of the mass of a component to the total mass. Mole Fraction: Ratio of the number of moles of a component to the total number of moles in a mixture. Volume fraction: based on the ratio of the volume of a pure component and the total volume of a solution at the same temperature and pressure. Parts per Million (ppm): A unit used to represent very small concentrations of a substance in a solution. Molarity: Number of moles of solute per liter of solution. Molality: Number of moles of solute per kilogram of solvent. Flow Rate: The rate at which material is transported through a process line, expressed as mass or volume per unit time. Mass flow rate is the mass of a material flowing per unit time. Volumetric flow rate is the volume of material flowing per unit time. If a material of density ρ flows through a pipe with cross-sectional area A at a velocity v Mass velocity G is the mass flow per unit cross-sectional area of flow Isothermal Process: A process operating under constant temperature conditions. Isobaric Process: A process operating under constant pressure conditions. Isochoric/isovolumetric: a system or process operating under constant volume condition. Adiabatic Process: A process where no heat is transferred to or from the surroundings. Batch Process: A process where the feed is added at the start, and the output is removed after a certain period. Continuous Process: A process where input and output flow continuously throughout the operation. Semi-batch process: Any process that is neither batch nor continuous.